This code

    225 if (text) {
    226 // rc = (jboolean)FcConfigAppFontAddFile(arg0, text);
    227 if (fp) {
    228 rc = (jboolean)((jboolean (*)(void *, const char *))fp)(arg0, text);
    229 }

is problematic for two reasons: jboolean is unsigned char, but FcBool is int, and arg0 is jlong, not void *, as the prototype suggests. The latter leads to build failures with future compilers.

The unsigned char/int difference may cause problems on certain platforms, depending on how the calling convention differ.